1. Field of the Invention
The invention relates to a positioning device, which comprises a base element and a carrier element, which can be positioned along a z-axis relative to the base element by displacing at least two slide elements transversely to the z-axis.
2. Description of the Related Art
Such a positioning device is known, for example, from U.S. Pat. No. 5,731,631. The device described there comprises a base and a carrier element having a working surface and two parallel-running wedge surfaces opposite the working surface. The carrier element is connected to the base by means of two spaced-apart vertical linear guides, which restrict the movement of the carrier element relative to the base to a displacement along the vertical z-axis. The positioning device further comprises as slide element two parallel-running wedges connected rigidly to one another, which are disposed between respectively one of the wedge surfaces of the carrier element and the base and which are connected to the base by means of two spaced-apart linear guides. By means of the two linear guides, the wedges can be moved along an x-axis perpendicular to the z-axis. In addition, the upper sides of the wedges are each connected displaceably to the wedge surface of the carrier element by means of a further linear guide. A linear motor is used to move the wedges along the x-axis whereby the carrier element is moved along the z-axis relative to the base. In this case, the two vertical linear guides between the base and the carrier element prevent the carrier element from co-moving additionally along the x-axis relative to the base during the movement along the z-axis.
For many applications in the area of high-precision positioning however, the system stiffness of such positioning devices with vertical linear guides is frequently not sufficient. In particular, a vertical linear guide does not ensure a sufficiently high rotational stiffness about the vertical axis. In addition, a design with displacement wedges and additional vertical linear guides is technically very complex and economically very expensive.
Furthermore, a positioning device with two parallel linear translation actuators is known from EP 1 911 551 A1, which are coupled to a carrier element to be positioned via two respective parallel oriented inclined thrust surfaces. Both thrust surfaces are inclined opposite to one another such that a synchronous displacement of both actuator axes causes a lifting or lowering of the carrier element. Both inclined thrust surfaces are formed by two respectively inclined linear guide rails disposed on opposite sides of the carrier element. However, using two parallel linear translation actuators is technically very complex and economically very expensive and requires a synchronization of both drives.